Last time PSU had soccer games on the regular in the big stadium, 60 people tops. At least that's how it looked.
Something that seats a minimum 5,000 with grass and therefore can be shared between Timbers2 and PSU would be an improvement, if it's on light rail somewhere not too far away. 5,000 is the magic number because it is US Soccer's second division minimum. Even then, that might be too big for PSU. Still, that scenario is not out of the realm of possibility, as the Timbers are going to want to limit the total number of games played in PP if/when grass is installed. Then again, the Timbers helping make a small expansion to Merlo at UP to get to 5,000 is also not out of the realm of possibility.
Or, as several USL stalwarts are trying to get the MLS-in-same-town-feeder-teams out of USL Championship and probably into USL League One, same concept doesn't even have to seat 5,000 (maybe 3,500). The strange part is where USL Championship just signed an expanded access deal with ESPN (there's been a game of the week on cable most weeks this year) because some of the standalone cities in the league are actually drawing people and viewers. So keep an eye out or something like that.